Q.
I'm a mother of a 10-year-old little boy who was just told that he has Intermittent Explosive Disorder. I have done some research on this and have yet to find a cause for this disorder. How did my son get this disorder? Was he born with it? Is it passed down from generation to generation?

A.
Your questions are perfectly understandable, in light of your son's receiving the diagnosis of IED. Unfortunately, the science has not quite caught up to your search for knowledge about this condition. Let's back up a bit, though.

Intermittent Explosive Disorder is one of the so-called "Impulse-Control Disorders, Not Elsewhere Classified" in the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th ed.). IED is characterized "?by discrete episodes of failure to resist aggressive impulses resulting in serious assaults or destruction of property?" (DSM-IV p. 609). The degree of aggressiveness is "?grossly out of proportion to any provocation or precipitating psychological stressor".

Very often, individuals with IED describe a build-up of tension before the aggressive behavior, followed by a sense of relief after the explosive act, which in turn may be followed by a period of guilt or remorse. The diagnosis of IED is not made if the behavior in question is better explained by another psychiatric (or medical) condition, such as a manic episode, brain trauma, etc. But IED, in all likelihood, represents a collection of different conditions with different underlying causes. That makes it hard to answer your question about inheritance of IED.

For example, some individuals with IED may show nonspecific abnormalities on their EEG (electroencephalogram or brain wave recording), whereas others do not. Some children with a diagnosis of IED may actually have undiagnosed or concomitant bipolar disorder (see, for example, McElroy et al, Are impulse-control disorders related to bipolar disorder? Compr Psychiatry 1996 Jul-Aug;37(4):229-40).

Regarding whether IED can be "passed down from generation to generation," I think the most honest answer is, "We don't know for sure, but there is no convincing evidence that it can be transmitted genetically." There simply have not been enough large-scale family studies using well-defined criteria for IED. However, there is some evidence that tempermental traits such as impulsivity may be genetically influenced--which does not mean it is passed down in the way blue eyes or blond hair are inherited.

For example, one study (Mattes & Fink, J Psychiatr Res 1987;21(3):249-55) obtained histories of first degree relatives on two groups: (1) patients with temper outbursts (N = 33), and (2) diverse psychiatric patients without temper outbursts (N = 12). Family interviews were conducted. Though the number of subjects was relatively small, and the results therefore preliminary, the study found evidence of familial transmission of temper problems. An average of 18.2% of Group 1 relatives had temper problems, compared to 4.3% for Group 2. However, the trait of having temper outbursts was more strongly transmitted than were specific diagnoses (e.g. Intermittent Explosive Disorder, Antisocial Personality Disorder or Residual Attention Deficit Disorder) associated with temper outbursts.

Patients with neurological conditions apparently related to their temper outbursts were less likely to have positive family histories. Also keep in mind that familial does not mean genetic, necessarily. Some problems run in families because of certain environmental or social factors, not because they are inherited.

Medications, such as anticonvulsant mood-stabilizers or SSRIs (Prozac and others) may also be useful in selected cases. So, rather than focusing on heredity, you may be better off trying to pinpoint any underlying and treatable disorders that may be affecting your son. Anything you can do to clarify this diagnosis with your son's doctor would be useful--and I would consider requesting a consultative second opinion with an expert in childhood psychiatric disorders.